bug#60531: 29.0.50; Some fixes and suggestions for the docstrings of treesit-parent-while and treesit-parent-until

["Daniel Martín via Bug reports for GNU Emacs, the Swiss army knife of text editors" <bug-gnu-emacs@gnu.org>]

The docstring of treesit-parent-while says:

Return the furthest parent of NODE that satisfies PRED.
Return nil if none was found.  PRED should be a function that
takes one argument, the parent node.

But, according to the source code, the first invocation of NODE passes
NODE itself, not its parent:

(let ((last nil))
    (while (and node (funcall pred node))

The same happens with the docstring of treesit-parent-until.

Another suggestion I have is that "the furthest parent of NODE" is a bit
ambiguous (furthest from NODE or from the root?).  I think it would be
more clear to say it will return the highest (ie. least deep) *ancestor*
of NODE.  In 37.3 Retrieving Nodes, we introduce the concepts of
"higher" and "lower" when explaining Tree-sitter nodes, so using this
terminology consistently would avoid confusion.